R12.1.3 - Issue parts to Suppliers and engage for only Services

Hi

We are on R12.1.3 and have the below scenario.

We sell custom made products(Service offerings) for our customers based on request. As part of the custom product make process ,we use some of the items stocked in our warehouse and also  engage suppliers for fabrication work only but supply the raw materials to the supplier.We pay the supplier only for the Fabrication activity and issue the raw materials to do this fabrication.

Once the fabrication activity is completed,supplier ships the end product to customer and informs us.We invoice the customer once the product has reached the Customer.